Process of oxidizing methyl groups in aromatic hydrocarbons.



. No. 780,4.04. V Patented January 17, 1905.

UNITED STATES PATENT OFFICE.

MAX BAZLEN AND HANS LABHARDT, OF LUDWlGSHAFENON-THE-RHINE,'

GERMANY, ASSIGNORS TO BADISCHE ANILIN UND SODA FABRIK', OF LUDWIGSHAFEN-ON-THE-RHINE, GERMANY, A CORPORATION. v

PROCESS OF OXIDIZING METHYL GROUPS IN AROMATlC HYDROCAIRBONS.

SPECIFICATION forming part of Letters Patent N 0. 780,404, dated January 17, 1905.

' Application filed September 22, 1903. Serial No. 174,175.

. obtained or, as-the case may be, the precipi- T0 aZZ whom, it may concern:

Be it known that we, MAX BAZLEN, a sub-' ments in Processes of Oxidizing Methyl Groups of Aromatic Hydrocarbons, of which the following is a specification.

We have discovered that manganese persulfate or, as it might be termed, the sulfate of manganese peroxid can be used for the oxidation of the methyl groups in aromatic hydrocarbons and derivatives thereof. The said manganese persulfate can, for instance, be obtained if manganous sulfate be treated in moderately-concentrated sulfuric-acid solution with electrolytic oxygen until the red solution of manganic sulfate, which is at first tate thereof tion.

We have discovered that the acid solution of manganese persulfate has the property of oxidizing the side chainsthat is, the methyl is converted into a brown soluor substituted methyl group-in aromatic hydrocarbons and their derivatives, so as to convert them into the aldehyde group. This new reagent acts in a different way from and is far better suited for use for this purpose than is a mixture of manganese peroxid and sulfuric acid. The reaction proceeds energetically under conditions under which manganese peroxid and sulfuric acid have practi: cally no action. The new process is of very general application.- Toluene gives a'good yield of benzaldehyde, and the homologues of toluene and its substitution products,-as also benzyl alcohol and its esters, behave similarly.

The process is of particular value for the production of orthonitrobenzaldehyde from orthonitrotoluene, for the yield of this body that can be obtained by the new process istwice as great as that hitherto obtained by the best-known process from orthonitrobenzalde hyde, manganese peroxid, and concentrated sulfuric acid.

If the oxidation be conducted more energetically-for instance, by the use of a higher temperature and a sufiicient quantity of oxidizing agentthe corresponding carboxylic acids can be obtained in some cases in admix ture with aldehydes.

The new process has the further advantage that the resulting sulfuric-acid solution of manganous sulfate can readily be converted by electrolytic oxidation into manganese per sulfate which can again be used, whereas it" has not generally paid to regenerate the manganese peroxid hitherto used when oxidizing with this reagent and sulfuric acid.

The following examples will serve to further illustrate our invention; but it is not confined 'to these examples. The parts are by weight.

Example 1: Prepare a solution of manganese persulfate, for instance, by electrolytically oxidizing a solution of six hundred parts of manganous sulfate (lWInSOi+4H2O) in twentynine hundred parts of' sulfuric acid, (containing about fifty-five per cent. of H2804.) This can be effected by using a lead anode and a cellfurnished with a diaphragm, keeping the temperature at from about to centigrade and using a current having a density of about fifteen to sixteen amperes per square decimeter at the anode and a tension of from four to four and a half volts. In this way a solution should be obtained containing from about twelve to fifteen percent. of manganese persulfate. Run this solution slowly during a period of from four to five hours into five hundred parts of orthonitro: toluene at a temperature of from 50 to 60 centigrade. Stir continuously during the addition and subsequently. When the solution is decolored, distil off the orthonitrobenzaldehyde formed and the excess of orthonitrotoluene in a current of steam. Conduct this operation preferably in such a Way that the sulfuric acid maintains its concentration.

Isolate the aldehyde from the distillate in the EV well-known manner. The sulfuric-acid solution of manganous sulfate remaining can at once be oxidized electrolytically and used again for a new operation.

Example 2: Prepare a solution of manganese persulfate as described in Example 1 and add to this three hundred parts of toluene. The addition is elfected gradually during a period of about fourhours while thoroughly stirring and maintaining the temperature at from about to 5O centigrade. Distil ofl" the benzaldehyde and toluene in a current of steam and separate the benzaldehyde in the usual Way. Benzoic acid is not produced under these conditions. The only by-product is very small quantity of resinous matter.

To produce benzoic acid, proceed as follows: Run thirty parts of benzaldehyde, while stirring thoroughly, into five hundred parts of a solution of manganese persulfate containing, say, nine-tenths per cent. of active oxygen. The reaction proceeds very slowly in the cold, and even at the temperature of the waterbath several hours are necessary. The yield is practically quantitative. Of course, if desired, the oxidation of the toluene to benzoic acid can be effected in one operation without the intermediate isolation of the aldehyde.

Example 3: Prepare an emulsion of about one hundred parts of benzyl alcohol and seven hundred and fifty parts of dilute sulfuric acid (containing fifty-five per cent. of H2801) by stirring the substances together with the aid of an effective stirrer. Add to this emulsion drop by drop five hundred and seventy parts of mangenese persulfate, (containing about seventy-nine hundredths per cent. of active oxygen.) The oxidation proceeds rap idly at a temperature of from 40 to centigrade. When the solution is decolorized,

drive off the benzaldehyde formed with steam. To separate the benzyl alcohol that passes over with it, the benzaldehyde can be converted into its bisulfite compound. The benzyl alcohol that is not oxidized can be recovered almost quantitatively. Only traces of benzoic acid are formed under the conditions described.

Example 4:: Mix together thirty parts of benzyl chlorid and seven hundred and lilty parts of sulfuric acid, (containing fifty-five per cent. of H2804.) Add to the emulsion gradually about one thousand parts of manganese-persulfate solution, (containing about seventy-nine hundredths per cent. of active oxygen.) Heat the mixture on the boilingwater bath. The oxidation occupies from three to four hours. A mixture is obtained of unchanged initial material, with benzoic acid as the principal product with a littlcbenzaldehyde. A small quantity of benzyl alcohol is converted into resinous products.

We claim-- 1. The process for the oxidation of the side chains in aromatic derivatives by treating them with an acid solution of manganese persulfate.

2. The process for the oxidation of the methyl group in orthonitrotoluene to the CH0 group by treating it with an acid solution of manganese persulfate.

In testimony whereof We have hereunto set our hands in the presence of two subscribing witnesses.

MAX BAZLEN. HANS LABHARDT. Witnesses:

JOHN L. HEINKE, JACOB ADRIAN. 

